CN1295709A - Optical data storage system with means for reducing noise from spurious reflections - Google Patents

Optical data storage system with means for reducing noise from spurious reflections Download PDF

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Publication number
CN1295709A
CN1295709A CN99804647A CN99804647A CN1295709A CN 1295709 A CN1295709 A CN 1295709A CN 99804647 A CN99804647 A CN 99804647A CN 99804647 A CN99804647 A CN 99804647A CN 1295709 A CN1295709 A CN 1295709A
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China
Prior art keywords
face
optical element
optical
fiber
refractive index
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CN99804647A
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CN1160715C (en
Inventor
J·P·维尔德
A·采利科夫
张永卫
V·伊兹拉利安
J·F·希纽
小J·E·赫斯特
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Seagate Technology LLC
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Seagate Technology LLC
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Priority claimed from US09/124,812 external-priority patent/US6298027B1/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
    • H04B10/2572—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to forms of polarisation-dependent distortion other than PMD
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/255—Splicing of light guides, e.g. by fusion or bonding
    • G02B6/2551—Splicing of light guides, e.g. by fusion or bonding using thermal methods, e.g. fusion welding by arc discharge, laser beam, plasma torch
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/262—Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4216—Packages, e.g. shape, construction, internal or external details incorporating polarisation-maintaining fibres
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
    • G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
    • G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
    • G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
    • G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
    • G11B11/10532—Heads
    • G11B11/10541—Heads for reproducing
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
    • G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
    • G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
    • G11B11/10532—Heads
    • G11B11/10541—Heads for reproducing
    • G11B11/10543—Heads for reproducing using optical beam of radiation
    • G11B11/10545—Heads for reproducing using optical beam of radiation interacting directly with the magnetisation on the record carrier
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1356—Double or multiple prisms, i.e. having two or more prisms in cooperation
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1362—Mirrors
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1365—Separate or integrated refractive elements, e.g. wave plates
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1365—Separate or integrated refractive elements, e.g. wave plates
    • G11B7/1369—Active plates, e.g. liquid crystal panels or electrostrictive elements
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1384—Fibre optics
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms
    • G02B6/4207—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms with optical elements reducing the sensitivity to optical feedback
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
    • G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
    • G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
    • G11B11/1055—Disposition or mounting of transducers relative to record carriers
    • G11B11/10552—Arrangements of transducers relative to each other, e.g. coupled heads, optical and magnetic head on the same base
    • G11B11/10554—Arrangements of transducers relative to each other, e.g. coupled heads, optical and magnetic head on the same base the transducers being disposed on the same side of the carrier
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
    • G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
    • G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
    • G11B11/1055—Disposition or mounting of transducers relative to record carriers
    • G11B11/1058—Flying heads
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1372—Lenses
    • G11B2007/13727—Compound lenses, i.e. two or more lenses co-operating to perform a function, e.g. compound objective lens including a solid immersion lens, positive and negative lenses either bonded together or with adjustable spacing

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Electromagnetism (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Optical Couplings Of Light Guides (AREA)
  • Optical Head (AREA)

Abstract

An optical data storage system utilizes optical fibers for transfer of information to and from storage media. The storage media comprise magneto-optical storage disks. The optical fibers are low-birefringence optical fibers. As compared with conventional approaches, a polarization state conveyed by the optical fiber is accurately reproduced with reduced noise. Various noise reduction techniques are provided by substantially decreasing or eliminating spurious reflections (or the effects thereof) at end faces and of an optical fiber. In particular, various techniques, such as index matching, a cover slip method, laser modulation, or angle polishing, may be used to eliminate spurious reflections (or the effects thereof) at the front end face of the optical fiber. Various techniques, such as angle cleaving, index matching, or multi-mode fiber splicing, may be used to eliminate spurious reflections (or the effects thereof) at the back end face of the optical fiber.

Description

Optical data memory system with device of the noise that reduction causes by parasitic reflection
Relevant application
The 60/079th of " using the optical drive of low birefringent fiber " by name that the present invention relates to propose on March 30th, 1998, No. 903 U.S. Provisional Patent Application, the 60/088th of " laser phase noise in optical drive minimizes " by name that proposed on June 5th, 1998, No. 192 U.S. Provisional Patent Application, the 60/108th of " eliminating the shaven head design of optical fiber end retroreflection " by name that proposed on November 13rd, 1998, No. 398 U.S. Provisional Patent Application, the 60/__ U.S. Provisional Patent Application of " fiber coupler of the polarization-maintaining fiber that use continues " by name that proposed on Dec 9th, 1998, and require right of priority, with their integral body by with reference to being incorporated in this.The present invention is that the part of the 09/124th, No. 812 U.S. Patent application of " low birefringent fiber that optical data memory system is used " by name that proposed on July 28th, 1998 continues, with its integral body by with reference to being incorporated in this.
Background of invention
1. invention field
The present invention relates generally to be used for the optical fiber of data-storage system, in more detail, the present invention relates to the low birefringent fiber in the magneto-optic data-storage system.
2. background technology
In magneto-optic memory systeml, use magneto-optic (MO) recording materials that are deposited on the rotary CD, can be recorded in the spatial variations of information on the magneto-optic disk as magnetic domain.Between reading duration, magnetic domain figure light modulated polarization, and detection system converts the signal that is produced to the electronics form from format optical.
In a class magneto-optic memory systeml, the magneto optical head assembly is placed on the linear-motion actuator, this actuator along the moving radially of magneto-optic disk, makes the magneto optical head assembly be positioned at the top of data track in record and reading duration chien shih magneto optical head.A magnetic coil is placed on the assembly that separates on the magneto optical head assembly, to be created in the magnetic field that magnetic-field component is arranged on the direction perpendicular to the magneto-optic disk surface., be that the magnetization sign zero as indication or of vertical polarization is recorded with respect to magnetic material at first around the magneto-optic disk medium by laser beam is focused on to form a luminous point on magneto-optic disk.The function of luminous point be make magneto-optic memory technique be heated near or surpass the temperature (apply magnetic field in this temperature and can easily change magnetization) of Curie point.The electric current that flows through magnetic coil makes the orientation of spontaneous perpendicular magnetization or upwards or downwards.This orientation process takes place in the light point area with suitably high temperature.After removing laser beam, keep the orientation of this magnetization.During magnetic coil produces rightabout magnetic field, if laser beam again this sign place spot heating to Curie point, then can wipe or rewrite this sign.
By utilizing the magnetic the Kerr effect according to the special sign sense information of being considered on the magneto-optic disk, thereby the magnetization of passing through the sign place that considered detects the gram ear rotation of the light polarization that is applied on the folded light beam.Determine the value (being included in the gram ear coefficient) of gram ear rotation by properties of materials.By the differential detection scheme set up and according to the direction in the spontaneous magnetization at the sign place that is considered is that orientation is measured sense of rotation clockwise or counterclockwise.
At present to have superficial density for the magneto-optic disk of the 1 gigabit bit per inch order of magnitude provides traditional magneto optical head of access certainly will be based on relatively large optical module, this assembly makes the physical size of magneto optical head and quality become rather heavy (generally being of a size of 3-15mm along a direction).As a result, mechanically mobile in the prior art magneto optical head is very slow with the speed that is accessed in the new data magnetic track on the magneto-optic memory disc.In addition, the physical size limitations of the magneto optical head of prior art the interval between the magneto-optic disk.Because available volume is limited in the calibrated altitude magneto optical driver, therefore, do not obtain magneto optical driver as yet as the high performance commercial prod of high power capacity.For example, present available commercialization magneto optical storage devices only provides the only access of one side of the two-sided 2.6 ISO GB magneto-optic disks of 130mm, and the magneto-optic disk access time is 40ms, and message transmission rate is 4.6 mbit/.
N.Yamada (the 5th, 255, No. 260 United States Patent (USP)s) has disclosed a kind of small-sized floating optic head, is used for the upper surface and the lower surface of a plurality of CDs of access.The floating optic head that Yamada discloses is described an actuator arm, and this arm has the mirror or the prism of static (fixing with respect to arm) mounted thereto, is used for light transmission is delivered to phase change disc and receives light from phase change disc.Though the static optical element that Yamada describes carries out access to the two sides that is included in a plurality of phase change discs in the fixed volume, the floating optic head of Yamada is subjected to the restriction of the size and the quality of optical element.As a result, also limited performance and the quantity that to make the CD that in giving constant volume, works.
Using polarization-maintaining fiber and Fabry-Perot (FP) laser instrument so that polarized light is delivered to from light source the application of memory location, Mode Partition Noise has limited available signal to noise ratio (S/N ratio).Be apparent that when the element high birefraction was placed in the light path of FP laser instrument, the Mode Partition Noise (MPN) of wideband polarization fluctuating form was the inherent characteristic of FP laser instrument.According to design, polarization keeps the birefraction of (PM) optical fiber very high, therefore, when PM optical fiber and FP laser instrument use together, is difficult to eliminate MPN.
Therefore, compare with traditional method, needed is a kind of optical data memory system with enough big signal to noise ratio (snr), described optical data memory system uses optical fiber, transmitting light between the memory location of LASER Light Source and optical drive, and the quantity that allows to be placed on to the disc in the constant volume increases.Preferably should provide bigger numerical aperture, less bare headed size and quality through improved shaven head.In addition, the shaven head noise that also should produce at access optical disc surface, CD drive access time, message transmission rate, optical mode and be easy to aim at and manufacture view improves to some extent than classic method.
Brief summary of the invention
By using low birefringent fiber to carry the information to optic storage medium and send information from optic storage medium, the present invention allows to increase and can be placed on any quantity of giving the storage disks in the constant volume.The tracking servo device of the high resonance frequency on less shaven head and optical fiber provide improved access to medium, improved disk drives access time and improved message transmission rate together.
According to the present invention, CD drive is used the various aspects of Winchester disk technology, for example, and the air supported head technology.In another aspect of this invention, from light source direct light switch, to being coupled to one of many low birefringent fibers of one or more pivot arms, each pivot arm supports a floating optic head to photoswitch to laser optic assemblies photoconduction light.In order to read and write the purpose of data with the luminous point of line focus at corresponding medium place, make light arrive corresponding shaven head by Optical Fiber Transmission.By shaven head and optical fiber the light signal through reflection from medium is coupled, is used for processing then.In another embodiment, the light source of light comprises stable single-frequency laser source, such as distributed feed-back formula (DFB) laser instrument.
By the steerable light path that changes the light that transmits by optical fiber through the mirror of little processing (micro-machined) that is installed on the air supported head.Center on turning axle rotation the carrying out search of track following and adjacent track by the middle body that makes mirror.By speck mirror (such as GRIN (graded index) lens or the moulded lens) guiding that embeds reflected light from steerable micro-machined mirrors.Make the luminous point of line focus come flyback retrace along the approximate direction radially that is parallel to memory disc.
In another embodiment, by operating one group of steerable micro-machined mirrors independent of each other, can carry out the search of track following and adjacent track to the surface of more than one medium.In this special embodiment, need a plurality of laser optic assemblies.
In another aspect of the present invention, use low birefringent fiber that information is delivered to the magneto-optic memory disc and spreads out of information from the magneto-optic memory disc.When the Optical Fiber Transmission, owing to be applied to inevitable stress on the optical fiber, may degenerate from the SNR ratio of the polarization information of medium.The invention provides the apparatus and method of a kind of SNR of raising.In one embodiment, compensation causes in birefringent (in-plane) crooked to increase SNR in low birefringent fiber.In another embodiment, compensation causes birefringent outer (out-of-plane) crooked to increase SNR.By the out-of-plane bending that provides the light polarization rotating element can compensated birefringence to cause, this element can comprise one 1/2 wave plate or the fixing quarter wave plate and the combination of variable phase wave plate.Can compensate in-plane bending by the light phase hysteresis that the light through reflecting is provided.Can provide phase lag by the light phase lag element, this element comprises: the combination of liquid crystal hysteresis device, fixing quarter wave plate and rotatable 1/2 wave plate or fixing quarter wave plate and rotatable polarization beam apparatus.In another embodiment again, can increase SNR by the light source that the light that comprises modulated Fabry-Perot or Distributed Feedback Laser is provided.
In another aspect of this invention, provide various reduction noise techniques by the parasitic reflection (or its influence) that reduces or eliminates in fact in the end of optical fiber.If lasing light emitter for example is FP or DFB lasing light emitter, then can use the technology that these reduce noise.Especially, can hold near (incident) before the optical fiber of lasing light emitter and eliminate parasitic reflection (or its influence) near (shaven head) end behind the optical fiber of medium.
As above narrate like the Noodles, (that is the influence of) parasitic reflection, incident end face can be modulated lasing light emitter with specific frequency, and this frequency depends on the length of optical fiber from the optical fiber front end face in order to eliminate.As a result, the parasitic reflection of optical fiber front end face is that main beam with the carrying signal that returns from medium separates in time.
In according to an alternative embodiment of the invention, by means of the optical fiber front end face is coupled to the parasitic reflection that a kind of material is eliminated the optical fiber front end face, the refractive index of this material equates with the refractive index of optical fiber fiber core.For example, this material can be made of epoxy resin, fluid or other suitable materials.
In according to an alternative embodiment of the invention, by means of the optical fiber front end face being coupled to the parasitic reflection that cover plate (coverslip) is eliminated the optical fiber front end face, the refractive index of this cover plate equates with the refractive index of optical fiber fiber core.For example, this cover plate can be made by glass or other suitable materials.
In according to an alternative embodiment of the invention, by means of by the influence of the optical fiber rear end face being polished the parasitic reflection of eliminating optical fiber rear end face (that is end surface) with respect to the special angle of light propagation axis.As a result, the main beam of carrying signal spatially separates with parasitic reflection.In addition, for best coupling efficiency is provided, can polish the grin lens that is coupled to the optical fiber front end face by similar angle with respect to the light propagation axis.
In according to an alternative embodiment of the invention, by means of by the influence of eliminating the parasitic reflection of optical fiber rear end face with respect to the special angle cutting optical fibre rear end face of light propagation axis.As the result of cut sth. askew (angle cleave), therefore parasitic reflection can not, be eliminated to coupling the back effectively effectively by optical fiber.
In according to an alternative embodiment of the invention, by means of the optical fiber rear end face being coupled to the parasitic reflection that a kind of fluid or epoxy resin are eliminated the optical fiber rear end face, the refractive index of this fluid or epoxy resin equals the refractive index of optical fiber fiber core.
In according to an alternative embodiment of the invention, by means of the optical fiber rear end face being coupled to the parasitic reflection that no fiber core or multimode optical fiber are partly eliminated the optical fiber rear end face, the refractive index of this fiber section equals the refractive index of optical fiber fiber core.For example, realize the coupling of optical fiber by welding (fusion splicing).
The accompanying drawing summary
Fig. 1 a illustrates an embodiment of the magneto-optic storage and retrieval system of the in-plane bending that has low birefringent fiber and out-of-plane bending;
It mainly is the magneto-optic storage and retrieval system of in-plane bending that Fig. 1 b illustrates what have low birefringent fiber;
Fig. 2 a illustrates laser instrument one optical module according to one embodiment of the present of invention;
Fig. 2 b illustrates an embodiment who is used to provide variable light phase lag;
Fig. 2 c illustrates another embodiment that is used to provide variable light phase lag;
Fig. 2 d illustrates another embodiment that is used to provide variable light phase lag;
Fig. 2 e illustrates an embodiment of light polarization spinner;
Fig. 2 f illustrates an embodiment, wherein uses the pulsed drive lasing light emitter;
Fig. 3 illustrates the optical module that comprises photoswitch;
Fig. 4 a-g illustrates the various views of air supported head of the present invention;
Fig. 5 a-b illustrates two embodiment of magneto optical driver;
Fig. 6 is the figure of optical fiber that has the grin lens of index-matching material according to being coupled to of an alternative embodiment of the invention;
Fig. 7 has figure with the optical fiber of the grin lens of the bonding cover plate of optical fiber according to being coupled to of an alternative embodiment of the invention;
Fig. 8 is the figure according to the folded light beam of the carrying signal that passes through grin lens and spread fiber of an alternative embodiment of the invention, and light beam has altered structure incident end face;
Fig. 9 a is the figure of the part of optical fiber, wherein, parasitic reflection occurs at the head end of optical fiber;
Fig. 9 b is a curve map, illustrates from the back relatively relation to coupling efficiency and optical fiber head end-grain cutting angle size of the fiber end face reflection of optical fiber head end;
Fig. 9 c illustrates a kind of optical system according to an alternative embodiment of the invention, and it has the optical fiber of cutting sth. askew downwards;
Fig. 9 d illustrates a kind of optical system according to an alternative embodiment of the invention, and it has the optical fiber of upwards cutting sth. askew;
Fig. 9 e illustrates a kind of optical system according to an alternative embodiment of the invention, the optical fiber that it is not cut sth. askew;
Figure 10 a illustrates a kind of optical fiber that comprises end surface according to an alternative embodiment of the invention, and it has vertical cut (straight cleave) or polishing, and is coupled to slide block with the fluid or the epoxy resin of refractive index match;
Figure 10 b illustrates the propagation and the parasitic reflection of the carrying signal light beam in the optical system shown in Figure 10 a;
Figure 11 a illustrates the optical fiber with head end according to an alternative embodiment of the invention, and this head end is connected with one section multimode optical fiber;
Figure 11 b illustrates the propagation and the parasitic reflection of the carrying signal light beam in the optical system shown in Figure 11 a; And
Figure 11 c is a curve map, is illustrated in the reflection of optical fiber head end and the relation of the length of the one section multimode optical fiber that is connected to this optical fiber.
The detailed description of preferred embodiment
Now in detail with reference to the accompanying drawings, wherein discern similar parts of the present invention, in Fig. 1 a, can see general with the magneto-optic storage and retrieval system 100 shown in the skeleton view with identical numeral.In one embodiment, magneto-optic (MO) data storage and retrieval system 100 comprises one group of Winchester type air supported head 106, and this air supported head is applicable to one group of two-sided first surface magneto-optic disk 107 (each air supported head in magneto-optic disk surface).By corresponding suspender 130 and actuator arm 105 air supported head group 106 (after this being referred to as the magneto optical head of floating) is coupled to revolving actuator magnet and coil block 120, thereby is positioned at the top on the surface of one group of magneto-optic disk 107.At work, consequently between unsteady magneto optical head group 106 and magneto-optic disk group 107, produce the aerodynamics raising force by Spindle Motor rotation magneto-optic disk group 107, keep quick condition at upper surface and the about 15 microinch places of lower surface from magneto-optic disk group 107 to cause the magneto optical head group 106 of floating.The equal opposite spring force that is applied by suspender group 130 resists raising force.At duration of work not, make the magneto optical head group 106 of floating remain on the store status on the surface of leaving magneto-optic disk group 107 statically.System 100 also comprises optical module 103 and the optical elements sets 102 (such as the low birefringent fiber group) that is coupled on it.
Fig. 2 a illustrates the laser instrument-optical module 101 that uses as the part of laser light module 103.In the present invention, the optical module 103 of Fig. 1 a and 1b comprises laser instrument-optical module 101, and this assembly comprises lasing light emitter 231, such as Fabry Perot (FP) laser instrument or stable single-frequency laser source, such as distributed feed-back (DFB) laser instrument.Owing in laser chamber, used optical grating element, so the DFB lasing light emitter produces highly stable arrowband single-frequency output with wavelength selectivity.In one embodiment, 231 work in about 660 nm wavelength places in the ruddiness zone of visible spectrum; Yet, be appreciated that work in other wavelength LASER Light Source also within the scope of the invention.The feature of Fabry-Perot laser diode is that the high frequency in their spectrum output rises and falls, and this will cause in the appearance that is referred to as Mode Partition Noise (MPN) in the art.When linearly polarized light being sent into high-double refraction element when (for example, the single mode polarization keeps (PM) optical fiber), Mode Partition Noise (MPN) shows with the form of polarization noise, and its effect is to reduce available signal to noise ratio (snr).In magnetooptic recording, because hope reads out the polarization information from magneto-optic disk 107, importantly to be retained to minimum to polarization noise, yet, inaccessible this requirement when using FP LASER Light Source and single mode polarization-maintaining fiber in the prior art.On the other hand, use low-birefringence (lo-bi) optical fiber to allow to construct the optical system that is difficult for having MPN.
As to be discussed below, for reduction or elimination provide the technology of various reduction noises at the parasitic reflection (or its influence) of the end of optical fiber 102 in fact.If lasing light emitter for example is FP or DFB, then can use these noise reduction technologies.
Laser instrument-optical module 101 further comprises: collimation optics 234, sew beam splitter 232 and coupled lens 233.Laser instrument-optical module 101 P polarized laser beam 291 from LASER Light Source 231 by sewing beam splitter 232 and coupled lens 233 direct light switches 104.Laser instrument-optical module 101 also receives S and the P polarized component through laser light reflected bundle 292 from the surface of specific magnetic CD 107.Coupled lens 233 guiding are sewed the difference detector that beam splitter 232 guiding comprise polarization beam apparatus 239, mirror 235 and photo diode sets 236 through laser light reflected bundle 292 and process.After through the conversion of photo diode sets 236 electro-optical signals, differential signal is through the processing of differential amplifier 237 and as signal 294 outputs.Differential signal measurement of difference detector 240 usefulness is through the S of the quadrature of laser light reflected bundle 292 and the luminous power of P polarized component, and the sensitivity that the polarization that described differential signal is preferably caused by the Kerr effect in the surface of specific magnetic CD 107 rotates is measured.As described below, in specific embodiments of the present invention, laser instrument-optical module 101 further is included in the multiple optical element of the position that AA and BB represent, lags behind and/or the light polarization rotation with the light phase that laser beam 291 and 292 are provided.
Fig. 3 illustrates the optical module 103 that comprises photoswitch 104.Photoswitch 104 is placed between optical fibre set 102 and the laser instrument-optical module 101, and shown in the representative light path that comprises one of one of optical fibre set 102, the magneto optical head group 106 of floating and one of magneto-optic disk group 107.Photoswitch 104 provides the selectivity of enough degree so that outgoing laser beam 291 is directed to the corresponding near-end of particular fiber 102.Outgoing laser beam 291 comes out and surface recording layer 349 by the corresponding magneto-optic disk 107 of magneto optical head 106 guiding that floats from the far-end of optical fiber 102.
During information write, outgoing laser beam 291 was by being heated to the coercive force that reduces surface recording layer 349 near the Curie point of magnetooptic recording layer 349 to the selected point of considering 340.The light intensity of outgoing laser beam 291 is remained unchanged, determine figure perpendicular to the magnetic domain of magneto-optic disk 107 " making progress " or " downwards " and become vertical off setting magnetic field when using.This technology is referred to as magnetic field modulation (MFM).Another kind of way is, in order preferably to control the domain wall position and to reduce the farmland edge shake, can modulate the mode that outgoing laser beam 291 becomes vertical off setting magnetic field when being synchronized with at point 340 places that considered.Then, when the selected point of considering 340 coolings, information is encoded on the surface of corresponding rotation disc 107 at superficial layer 349 places.
Between the reading duration of information, selectively outgoing laser beam 291 (is compared with the power that writes, its power is lower) be sent to magneto-optic disk 107, cause at point 340 reflex times from being considered, the Kerr effect causes through the polarization state of laser light reflected bundle 292 or turns clockwise or inhour rotation (shown in arrow 363).Above-mentioned in fact light path is two-way.Correspondingly, receive and be input to the far-end (head end) 900 of optical fiber 102 by the magneto optical head 106 of floating through laser light reflected bundle 292.Optical fiber 102 is used for electro-optical signal conversion then being sent to laser instrument-optical module 101 selectively through laser light reflected bundle 292 direct light switches 104 and by photoswitch 104.
Get back to Fig. 1 a, in preferred embodiment, optical fibre set 102 of the present invention comprises the single mode low birefringent fiber.The present invention determines, is designed to have the optical fiber (being called low-birefringence (or lo-bi) optical fiber in optical fiber technology) of low-birefringence by use, can reduce Mode Partition Noise to obtain acceptable signal-to-interference ratio (SNR).The intrinsic high birefringence of the low-birefringence of lo-bi optical fiber and single mode polarization-maintaining fiber (being also referred to as PM optical fiber) compares.Can provide lo-bi optical fiber as " spin fiber " (spun fiber), it is to form from birefringence fiber prefabricated rods rotation a little during fiber draw process.When cooling, make how much reverse be fixed into spin fiber.If the specific rotation of optical fiber is enough big, then can overwhelm crooked straight line birefringence that produces or because the birefringent effect that the anisotropy thermal stress produces by the equivalent garden birefringence of introducing by rotation.Most of single-mode fibers present the straight line birefringence to a certain degree that is caused by local internal stress.Spin fiber is a kind of exception, this means, prefabricated rods is rotated rapidly, can produce a kind of average effect, and for the spread length that strides across several swing circles, it will cause low inherent straight line birefringence.Being appreciated that the present invention needn't be limited to the lo-bi optical fiber of rotation, also is being known because use other technology (for example, prefabricated rods that carefully designs and special drawing technology) to make lo-bi optical fiber in the art.In an exemplary embodiment of the present invention, lo-bo optical fibre set 102 comprises: but the mode field diameter of the operating temperature range of the two sheaths of the acrylates of the cladding diameter of the cutoff wavelength of the phase lag of every meter 1-2 degree, the operation wavelength that is similar to 600 nm, 580-600 nm, about 80 μ m, diameter 160-190 μ m, 0-70 ℃, about 4.0-μ m and less than 5% mode field ovality.
As shown in Figure 1a, lo-bi optical fibre set 102 in magneto optical head group 106 is floated in the coupling of its far-end corresponding one group, the route of determining this optical fibre set determines that along in actuator arm group 105 and the suspender group 130 corresponding one group its route is coupled to optical module 103 around optical module 103 and in its proximal end.Because the added restriction of the finite volume in system 100, optical fibre set 102 may require not to be that conllinear and/or coplane mode are determined its route, this then can make optical fiber 102 be subjected to stress, therefore produces birefringence in optical fiber 102.Optical fiber 102 shown in A point place come out from optical module 103, and gather together and center on optical module 103 and twine.If desired, extra winding provides extra fiber lengths so that assemble and reprocess.Preferably determine the route of optical fiber like this, that is, most bending all occurs in the single plane and (after this is referred to as (in-plane) bending in the face).The example of the in-plane bending of optical fiber 102 is shown at a C place.Optical fiber 102 fan-outs (fan out) are to its head separately on some point, for example shown in some B place begin; Therefore, also have (out-of-plane) bending outside some faces between optical fiber 102, this can change birefringent local orientation, if but keep enough big bending radius, then the outer birefringent value of face can be quite little.The birefringent feature that bending causes can be expressed as: (1) is proportional to (R Fiber/ R Bend) 2Value, wherein a R FiberBe the radius of fibre cladding and R BendIt is crooked radius; And (2) a kind of like this orientation, cause an axle in the plane of bending and another root axle perpendicular to this plane.If not the bending because of optical fibre set 102, output and laser light reflected bundle 291 and 292 stand to have the optical fibre set 102 of low-birefringence in theory, are similar to one group of free space light path.Yet the above-mentioned bending that the birefringence in lo-bi optical fibre set 102 causes can make the polarization rotation information that transmits by optical fibre set 102 degenerate.Correspondingly, in one aspect of the invention, provide a kind of method and apparatus that is used to compensate, be included in the optical element in the light path of laser beam 291 and/or 292, to provide light phase to lag behind and/or the light polarization rotation.
Can determine according to the present invention, the birefringence that bending by optical fibre set 102 causes, between the S of laser beam 292 and P polarized component, introduced phase shift, and determine, can compensating phase shift by in the light path of folded light beam 292, placing the light phase lag element, determine in addition,, should keep 0 degree mould π (0 degrees modulo π) in the P and the phase shift between the S polarized component of the reflection of laser beam 292 for gram ear rotation with the SNR detection of reflected laser beam 292 of maximum.In a preferred embodiment, utilize the light phase lag element by making reflection lasering beam 292 and cross polarization gram ear component homophase when not restraining the ear signal, to optimize gram ear signal from magneto-optic disk 107.By in the work of the bottom of noise fringe (noise fringe), do that like this Mode Partition Noise of being introduced by optical fibre set 102 is minimized.Can provide light phase to lag behind by the light phase lag element, this element makes light wave resolve into two orhtogonal linear polarizaiton components and produce phase shift between them.Ideally, provide the optical element of optical retardation will be neither can polarization also can not cause Strength Changes during by them at light beam; They will change the polarization state of light beam simply.The element that provides light phase to lag behind can be that fix or variable kind, and generally can be used as birefringence, uniaxial material with two different refractivities and obtain.Several examples of for example enumerating this material can comprise uniaxial crystal, quartz crystal, mica crystal, nematic liquid crystal, electrooptical material, polymkeric substance.
Can determine that according to the present invention in order to obtain these situations, the axle that the bending of optical fibre set 102 causes preferably should be aimed at the axle of sewing beam splitter 232, cause the P polarization of outgoing laser beam 291 will be parallel to the axle that the in-plane bending by optical fibre set 102 causes.
As mentioned above, optical fibre set 102 may experience bending, for example, and the combination of in-plane bending and/or out-of-plane bending.In another embodiment shown in Fig. 1 b, can determine the route of optical fiber 102 like this, cause the out-of-plane bending of the minimum that optical fibre set 102 takes place, for example, make it to come out and make it to be kept if determine the route of optical fiber 102 along parallel plane from optical module 103, then the interplanar that has of these parallel planes every and 106 (they not being fan-out) separately that arrive of the route of optical fiber at B point place between and the interval equate.In this embodiment, even without out-of-plane bending, the in-plane bending of optical fiber can take place still, such as optical fibre set 102 from optical module 103 to the end 106 normal determine route during.
The birefringence that causes for compensated bend and need light phase to lag behind takes place among the embodiment of minimal face outside sweep at optical fiber 102.Can provide this compensation by a light phase hysteresis device 255, this light phase hysteresis device comprises the variable liquid crystal hysteresis device such as the LVR 100VRS of the Meadowlark Optics manufacturing of state of Colorado Frederick.In this embodiment, light phase hysteresis device 255 uses together with the one 1/2 wave plate 253, and the both is placed on the BB point place (shown in Fig. 2 a and 2b) in the light path of sewing between beam splitter 232 and the polarization beam apparatus 239.Preferably the optical axis of light phase hysteresis device 255 with respect to the optical axis alignment of sewing beam splitter 232 at zero degree, and the optical axis of the one 1/2 wave plate with respect to the optical axis alignment of polarization beam apparatus 239 at 22.5 degree.This set of 1/2 wave plate makes polarization rotate about 45 degree, thereby produces the power that equates when not restraining ear signal (that is equilibrium state) on photoelectric detector.In a kind of use of variable liquid crystal hysteresis device, apply from about 0.1 volt of peak-peak input voltage to about 10.0 volts of scopes, it has illustrated for the stress that causes in the face and has produced suitable compensation; The in-plane bending that changes a little between the optical fibre set 102 may require slightly different voltage.The special voltage that when can the pre-settled use special optical fiber 102 of calibration phase, will apply.Can change this voltage during the time interval between photoswitch 104 switches.
Take place among another embodiment of minimal face outside sweep at optical fiber 102, can provide light phase to lag behind by the quarter wave plate 254 of combination traditional type and 1/2 wave plate 257 of dynamically rotation, the both be placed on and sews (shown in Fig. 2 a and 2c) between beam splitter 232 and the polarization beam apparatus 239.In this embodiment, the optical axis of quarter wave plate 254 with respect to the optical axis alignment of sewing beam splitter 232 at 45 °, and dynamically the optical axis of 1/2 wave plate 257 of rotation with respect to the optical axis rotation of sewing beam splitter 232.Dynamically 1/2 wave plate 257 of rotation can comprise and is coupled to 1/2 wave plate dynamo-electric or electricity-micro-machined actuator, to start the rotation of desired 1/2 wave plate.When using special optical fiber 102, can be in the predetermined special rotation that will be applied to 1/2 wave plate 257 of calibration phase.Can during the time interval between the switching of photoswitch 104, apply rotation.
In yet another embodiment, provide light phase to lag behind by quarter wave plate 254, this quarter wave plate is placed on sews between beam splitter 232 and the polarization beam apparatus 239, preferably the optical axis of quarter wave plate 254 with respect to the optical axis alignment of sewing beam splitter 239 at 45 ° (shown in Fig. 2 a and 2c).Under this pattern, the dynamic gyrator assembly of photoelectric detector conduct that polarization beam apparatus 239 is provided and is associated with it.Dynamically the gyrator assembly can comprise and is coupled to polarization beam apparatus and photo-detector block dynamo-electric or electricity-micro-machined actuator, to start the rotation of desired sub-component.When using special optical fiber 102, can during calibration phase, be scheduled to the special rotation that will apply, and can during the time interval between the switching of photoswitch 104, apply rotation.
In the above-described embodiments, though compensation is the stress that static in-plane bending causes in low birefringent fiber, can ignore the stress that dynamic in-plane bending causes, because generally speaking it is very little, though also can it be compensated in principle with enough fast compensation.
In the embodiment of above-mentioned Fig. 1 a, determine that the route of every optical fiber of optical fibre set 102 centers on the floating optic head 106 that optical module 103 arrives separately.The route of determining optical fiber 102 causes every optical fiber to advance with slightly different paths to shaven head 106 separately, therefore, stands different out-of-plane bendings with respect to output point A.Out-of-plane bending causes every lo-bi optical fiber 102 to comprise the axle that bending causes, their each other orientations and/or slightly different for the orientation of sewing beam splitter 232.By using light polarization spinner 256 can make the variation between the axle that the out-of-plane bending of every optical fiber 102 causes compatible, can this light polarization spinner 256 of dynamic adjustments with the linear polarization of rotation outgoing laser beam 291, for example, to spend the quarter wave plate hysteresis device of a kind of traditional type of coupling with respect to the axle 45 of the second variable liquid crystal hysteresis device (being shown in Fig. 2 e).Can obtain the polarization rotation by the hysteresis of electrically controlling variable liquid crystal.Can be with the LPR100 660 of the Meadowlark Optics of state of Colorado Frederick as aforesaid variable light polarization rotator.Also can be by machine-electricity rotation startup light polarization spinner 256 of 1/2 wave plate.During aligning step, can determine to aim at the caused needed polarization rotation amount of axle of every optical fiber 102, cause in operation, when occurring in when switching between the optical fiber 102, being applied to light polarization spinner 256 so that needed polarization rotation to be provided with the form of feedforward corresponding to the control voltage of the special optical fiber 102 that is using.
When not having the in-plane bending of above-mentioned optical fiber 102, among the embodiment such as the bending that keeps minimum in the light path that optical fiber 102 is advanced, light phase lags behind optional.When not having the out-of-plane bending of above-mentioned optical fiber 102, such as only single lo-bi optical fiber 102 carefully being placed the Plane Installation anchor clamps and communicating information to an embodiment of single magneto-optic disk 107, light polarization is rotated optional.In face occurring and among outer two kinds of another embodiment of bending of face, may need light phase hysteresis and light polarization to rotate both.Therefore should be understood that the present invention to be not limited to the foregoing description and be only limited to the scope of following claims.
The fiber end face reflection
In another embodiment that Fig. 2 f describes, determine, parasitic reflection from optical fibre set 102 near-ends (incident end) can reduce SNR, thereby folded light beam 292 may propagate with the folded light beam 291 from near-end 615, thereby causes comprising in folded light beam 293 E (t)+E (t+ τ).In this case, lasing light emitter 231 for example can be Fabry-Perot (FP) type, with dutycycle be 50% or littler pulse this LASER Light Source is switched on and off, and its modulation frequency range is from about 200 MHz to about 1.0GHz.In addition, the present invention is definite, with more and more higher frequency (for example, high relaxation oscillation frequency) the FP laser instrument is applied pulse to laser instrument, to make the Mode Partition Noise in the optical system reduce gradually, because under higher frequency, change have taken place in the lasing mode distributed power.Laser instrument 231 (the FP type) is applied reflected impulse that pulse allows light beam 293 separate with the main beam 292 of carrying signal in time, thereby reduce two interference between the spike train and so and increase the SNR of detected gram ear signal effectively.So, can increase Mode Partition Noise and laser phase noise allowing two light beams on the time in the overlapping and situation of interfering.
In one embodiment, the refractive index of optical fiber 102 is 1.5, for the modulating frequency that is about 350MHz, selects the length of every optical fiber 102 to be about 71.35 mm.Pass between the length (L) of modulating frequency (F) and optical fiber 102 ties up in the equation and embodies: F=c (2i+l)/4Ln, and i=0 here, 1,2 ..., the c=light velocity, the refractive index of n=optical fiber.Select the length of optical fibre set 102 to separate with the reasonable time that guarantees spike train.Being appreciated that in other embodiments can be according to other refractive index and other the pulsed frequency length of selecting optical fiber 102, and therefore, the present invention only is subjected to the restriction of the scope of claims.Though the present invention describes the use of low birefringent fiber, but be appreciated that, using high birefringence optical fiber (for example, polarization-maintaining fiber among) the embodiment, also can apply pulse and select suitable fiber lengths to increase SNR laser instrument with aforesaid.
Fig. 4 a-g illustrates the various views according to the magneto optical head of embodiments of the invention.Can the magneto optical head group of floating be described with reference to single representational unsteady magneto optical head 106.In single representational unsteady magneto optical head 106 shown in Fig. 4 b, above the corresponding surface recording layer 349 that one of be placed on it in the magneto-optic disk group 107 of rotation.In preferred embodiment, the magneto optical head 106 of floating comprises: main body 444, air-supported surperficial 447, steerable micro-machined mirror assembly 400, object optical element (objective optics) 446 and magnetic coil 460.In one embodiment, magnetic coil 460 is near the miniature multiturn coils that are placed on air-supported surperficial 447, so that produce such magnetic field: every kind of about 300 oersteds of polarity, can be in the time of about 4ns oppositely, and approximately perpendicular to the plane of the magneto-optic disk 107 that rotates.In the common U.S. Patent application of transferring the possession of 08/844,207, described the example of suitable steerable micro-machined mirror assembly, quoted the integral body of this application at this by reference.Be preferably in the interference that is not subjected to magnetic coil by float magneto optical head 106 output and reflection lasering beam 291 and 292 in the way of rotation magneto-optic disk 107, vice versa.As the mechanical dimension and/or the optical characteristics of said elements that comprises the magneto optical head 106 of floating, main body 444 is determined, comprises the height of about 889 μ m and corresponding to the plane areal coverage (footprint area) of 2032 μ m * 1600 μ m.Preferably low birefringent fiber 102 is coupled to and floats magneto optical head 106 and make it to keep axle along main body 444 by the suitable passage of making cun of v shape groove 43 or other.Optical fiber 102 is placed in the v shape groove 443, preferably outgoing laser beam 291 as the point of being considered 340 of optimum focusing and be directed to magneto-optic disk 107.Then can be optical fiber 102 fix in position by use ultra-violet curing epoxy resin or similar cementing agent.The optical fiber 102 of use in v shape groove allows to aim at and transmit outgoing laser beam 291 exactly with respect to mirror assembly 400.Steerable micro-machined mirrors sub-component 400 and object optical element 446 be miniaturization and little quality preferably, so that can be installed in the physics volume of approximate definite main body 444 rectangular profile sizes, but also enough greatly to aim at the complete xsect of output and reflection lasering beam 291 and 292, so that the power loss minimum, and in output and reflection lasering beam 291 and 292, do not introduce tangible distortion and chromatic dispersion.The low birefringent fiber 102 of the application of the invention, the profile of magneto optical head 160, weight and design all obtain simplifying further: do not need to use quarter wave plate as additional optical element on the magneto optical head 106 of floating, and just need this additional optical element when using polarization-maintaining fiber.
Be preferably in and aim at steerable micro-machined mirrors sub-component 400 in the representational light path,, consequently reflection lasering beam 292 is turned back to laser instrument-optical module 101 from magneto-optic disk 107 guiding to cause outgoing laser beam 291 by object lens 446 guiding magneto-optic disks 107.In one embodiment, object lens 446 can be the lenticules (mierolens) with about 0.6-0.85 numerical aperture (NA).Owing to remain quite constant value in air-supported lip-deep flying height, so no longer need focus servo.
When in magneto-optic storage and retrieval system 100, using, reflection central mirror part 420 by making steerable micro-machined mirror assembly 400 (shown in broken lines in Fig. 4 a covered) to show around a turning axle rotation that is subjected to 410 constraints of one group of hinge carry out near the meticulous tracking and the short search of magnetic track, cause the angle of propagation that before being transferred to object lens 446, changes outgoing laser beam 291.Make reflection central mirror part 420 wind the axle rotation that forms by hinge 410 by differential voltage being applied to drive electrode.Differential voltage produces an electrostatic force, and this power radially 450 moves the point of being considered 340 of line focus on magneto-optical media 107.In one embodiment, central mirror part 420 is rotated+/-2 degree approximately, and this is equivalent to approximately at lip-deep+/-4 of magneto-optic disk 107 magnetic track.Though in example embodiment, disclosed+the moving of/-4 magnetic tracks, according to above-mentioned steerable micro-machined mirror 400 desired performance characteristics, be appreciated that to be greater than or less than+moving range of/-4 magnetic tracks also is possible.As a result, can cross that magneto-optic disk 107 moves to the point of being considered 340 of line focus and the detection of reflection lasering beam 292 is used to store and retrieving information, track following and the search from a data magnetic track to another data track.(Fig. 1 a) can keep thick tracking with revolving actuator magnet and coil block 120 by regulating electric current.Known routinely, use the track following signal that can obtain being used to following the tracks of the special magnetic track of magneto-optic disk 107 in conjunction with the thick and thin servo techniques of following the tracks of.For example, can use sampling sector servo form to determine magnetic track.Servo format can comprise impression pit that is embossed on the magneto-optic disk 107 or the magnetic domain of reading similar in appearance to Data Labels orientation.If use the impression pit, then can use a totalizer output circuit to replenish differential amplifier 237 (Fig. 2).Traditional many disks Winchester disk driver use one group separately suspender and actuator arm make it as an integral unit and synergistically (in tandem) move.Because each air supported head of this integral unit is fixed with respect to other air supported head, therefore, during the track following on particular disk surface, can not follow the tracks of the magnetic track of other magnetic disk surface simultaneously.Under the contrast, no matter whether moving of actuator arm group 105 and suspender group 130, can use one group of steerable micro-machined mirrors sub-component 400 to operate independently, therefore allow track following and search, so that can use more than one magneto-optic disk surface to read and/or writing information in any given moment.Use the independently track following of one group of steerable micro-machined assembly 400 of operating simultaneously and read-out channel separately and meticulous tracking electronic circuit and the mirror driving electronic circuit that search preferably requires a component to open.Because the foregoing description preferably requires to use laser instrument-optical module 101 separately, so do not need to be used for the photoswitch 104 that between each light path of separating, switches.
Fig. 5 a illustrates the magneto-optic data storage and retrieval system as the part of magneto optical driver.In one embodiment, magneto-optic system 100 comprises miniature high-speed and high power capacity magneto optical driver 500, described magneto optical driver comprises 5.25 inch half height of industrial standard shape coefficient (form factor) (1.625 inches), at least 6 two-sided magneto-optic disks 107 and at least 12 unsteady magneto optical head 106.As mentioned above, can make the magneto optical head 106 of floating and make it to comprise the part of optical fiber 102 as minimum quality, little profile, high-NA optical system, in the very approaching interval of magneto optical driver 500, use a plurality of magneto-optic disks 107 with activation, therefore, compare with the equal volume according to classic method, it allows to comprise bigger area and capacity volume and memory capacity.In one embodiment, the interval between each magneto-optic disk 107 is less than or equal to 0.182 inch.Can determine according to the present invention, can transmit polarization state by low birefringent fiber 102, this noise when transmitting by polarization-maintaining fiber is little.
In another embodiment shown in Fig. 5 b, half height shape coefficient magneto optical driver 500 can comprise dismountable magneto-optic tray salver part 510 and two fixing inner magnet CDs 107.By dismountable magneto-optic tray salver part 510 is provided, fixing inside allow effectively external information to be sent to magneto optical driver 500 with dismountable combination, then to be sent to inner magnet CD 107.Then can write down back the information of duplicating on dismountable magneto-optic tray salver part 510, be used to be assigned to other computer system.In addition, dismountable magneto-optic tray salver part 510 allows extremely convenient and carries out the backup of inner magneto-optic rotating disc 107 at high speed.Fixing also the allowing storing data files on dismountable magneto-optic tray salver part 510 of inside with dismountable combination and on inner magneto-optic rotating disc 107 storage system file and software application.(not shown) in another embodiment, magneto optical driver 500 can comprise: the magneto-optic disk 107 of the inner magnet CD 107 of any number (comprising zero) and/or any number in dismountable magneto-optic tray salver part of any number.
According to the present invention, need not use the revolving actuator arm.For example, can use the linear-motion actuator arm.Can use little profile light path that the present invention discloses that information is sent to the memory location and send, and not need discrete object optical element (for example, use conical fiber or at one end form the optical fiber of lens) from the memory location.
As above illustrate like the Noodles, when interfering, can increase undesired laser noise from the parasitic reflection of the conjugate points in the optical system and reflection lasering beam 292 (Fig. 3).Conjugate points comprises the front end face (incident end 615) and the rear end face (head end 900) of optical fiber 102.Especially, (Fig. 2 undesired laser noise will occur a) and when parasitic reflection and reflection lasering beam 292 hypothesis have approximately uniform space distribution when spreading into difference detector 240 from the parasitic reflection of conjugate points with carrying signal reflection lasering beam 292.So before parasitic reflection generally produced a reflection wave, it was spatially very closely overlapping with the reflection lasering beam 292 from the recording layer 349 of magneto-optic disk 107.
Be used to reduce the RF modulation of the influence of optical fiber input end 615 reflections
As explained above, can modulated laser source 231 to reduce the noise in the optical system by the way that the reflection 292 (from magneto-optic disk 107) of parasitic reflection E (t) (from optical fiber input end 615) and carrying signal is separated in time.Therefore, reduced the interference between two folded light beams, improved thus by the difference detector 240 (SNR of the gram ear signal that Fig. 2 a) detects.As also illustrated in the above, lasing light emitter 231 for example can comprise FP laser instrument or stable single-frequency laser (such as Distributed Feedback Laser).
According to the present invention,, additional technology is discussed now for the influence of the parasitic reflection of the incident end 615 that reduces optical fiber 102.These additional technology comprise refractive index match, cover plate technology and tiltedly polishing (angle polishing).By use lasing light emitter 231 (for example, it can be the FP laser instrument or such as the stable single-frequency laser of Distributed Feedback Laser), can carry out these additional technology.
Be used to reduce the refractive index match of the influence of optical fiber input end 615 reflections
Also can use the refractive index match technology to reduce influence from the parasitic reflection of the incident end 615 of optical fiber 102.In one embodiment, optical fiber 102 (or fibre bundle) is coupled to grin lens 610, to form collimating apparatus (container) 600, as shown in Figure 6.A kind of index-matching material 605 is filled in the space between grin lens 610 and the optical fiber 102.Optical fiber 102 in the kapillary 602 supporting collimating apparatuss 600.Use grin lens 610 to enter the optical fiber fiber core, and can have for example about 0.23 gradient (pitch) so that incoming laser beam is focused on through the incident end 615 of optical fiber 102.The refractive index of index-matching material 605 equals or near equaling the refractive index of the fiber core of optical fiber 102, eliminates thus or reduces from incident end 615 surfaces significantly and the Fresnel reflection of grin lens surface 609 (in the refractive index of grin lens substantially under the condition near the refractive index of optical fiber 102) internally.Index-matching material 605 for example can comprise optical resin, gel or fluid.Under the unmatched condition of refractive index of the refractive index of the fiber core of optical fiber 102 and index-matching material 605, the refractive index difference that can allow Δ n=+0.05 between optical fiber 102 fiber cores and index-matching material causes about 0.03% surface reflections rate maximal value thus.Index-matching material 605 preferably has high optical quality, to avoid aberration or scattering.In addition, air one plane of incidence 608 the most handy antireflection (AR) coatings of grin lens 610 cover, further to reduce reflection.The AR coating for example is that any suitable thin film dielectric that is used to reduce to reflect is piled layer.
Note,, reflection still occurs at this incidence surface place from certain size of outgoing laser beam 291 even air-incidence surface 608 usefulness antireflection coatings cover.If emitting laser bundle 291 is incident upon air-incidence surface 608 with desirable normal incidence, then can be overlapping with the folded light beam 292 of carrying signal in the reflection of the outgoing beam at surperficial 608 places.Yet the probability that outgoing laser beam 291 will be incident upon surface 608 with desirable normal incidence is very little.Generally, among each embodiment of Jie Shiing, emitting laser bundle 291 will be incident upon surface 608 with certain incident angle owing to following result in the above.For the end 615 of injecting that is associated of the every optical fiber 102 in the fibre bundle of the optical system of Fig. 6 focuses on or guided laser bundle 291 suitably, laser beam 291 will be incident upon air-incidence surface 608 with different incidence angles, and this incident angle depends on the coordinate of the specific incident end 615 that receives laser beam 291.
As shown in Figure 6, index-matching material 605 makes parasitic reflection not appear at optical fiber input end 615 places.And parasitic reflection E (t) will appear at index-matching material and grin lens 610 between non-conjugated surperficial 609 places (that is, refractive index difference occurring) at interphase place in this surface.As a result, parasitic reflection E (t) is spatially not overlapping with the light beam 291 of carrying signal, thus also not with folded light beam spatially overlapping (Fig. 3) from the carrying signal of magneto-optic disk 107 reflection.Because parasitic reflection E (t) spatially separates with the folded light beam 292 of carrying signal, thus difference detector 240 (Fig. 2 a) can detect the folded light beam 292 of carrying signal and produce not interfere with parasitic reflection E (t).
On the contrary, if index-matching material is not coupled to incident end 615, then in the interphase between the air space of optical fiber input end 615 and vicinity refractive index difference can appear.As the result of this refractive index difference, the parasitic reflection E (t) that produces at optical fiber input end 615 places will be spatially overlapping with the folded light beam 292 of carrying signal.So this undesired parasitic reflection E (t) has been sent into difference detector together with the folded light beam of carrying signal, and (Fig. 2 a).
Be used to reduce the cover plate technology of the reflection of optical fiber input end 615
Fig. 7 illustrates and is used to reduce another kind of refractive index match method in the influence of the parasitic reflection at incident end 615 places of optical fiber 102 according to an alternative embodiment of the invention.Collimating apparatus 750 comprises grin lens 715 and cover plate 700, and this cover plate is coupled to optical fiber 102 and/or to the kapillary 755 that supports optical fiber.Cover plate 700 comprises the back side 765, generally for example uses this back side and optical fiber 102 (and with kapillary 755) a kind of optical adhesive bonding, and the refractive index of this optical adhesive equates with the refractive index of cover plate.Cover plate 700 can be with making such as glass or other suitable materials.
Fig. 7 also illustrates, and cover plate 700 makes parasitic reflection E (t) not appear at optical fiber input end 615.And parasitic reflection E (t) will appear at 760 places, surface (non-conjugated point) of cover plate 700.As a result, parasitic reflection E (t) not with folded light beam spatially overlapping (Fig. 3) from the carrying signal of magneto-optic disk 107 reflection.Because parasitic reflection E (t) spatially separates with the folded light beam 292 of carrying signal, thus difference detector 240 (Fig. 2 a) can detect carrying signal folded light beam 292 and not with parasitic reflection E (t) interference.
In another embodiment, the front surface 760 of cover plate 700 also can adopt AR to apply, with the Fresnel reflection that reduces at surperficial 760 places.For example, the reflectivity of the front surface 760 that applies from AR is at about 0.25% the order of magnitude.
Replace as another kind, grin lens 715 also can adopt AR to apply, further to reduce the reflection in the optical system among Fig. 7.Because the refractive index of cover plate 700 (and bonding agent is installed accordingly) select substantially with the refractive index match of the fiber core of optical fiber 102, appear at unique injection in the optical system from the prominent front surface 760 that covers of the AR of cover plate 700.Because front surface 760 does not comprise the conjugate points in the optical system of Fig. 7, therefore, as mentioned above, from the parasitic reflection E (t) of front surface 760 not with light beam 292 interferences of carrying signal.
Be used to reduce the oblique polishing of influence of the reflection of optical fiber input end 615
An alternative embodiment of the invention is installed, can uses oblique finishing method to reduce influence from the parasitic reflection E (t) of the incident end 615 of optical fiber 102.If lasing light emitter 231 is for example implemented with FP laser instrument or DFE laser instrument, then can use oblique finishing method.As shown in Figure 8, grin lens 800 is done tiltedly polishing at surperficial 805 places, thereby grin lens 805 is set in mode with respect to light propagation axis 807 values of acutangulating 809.Can to the angular range of about 15 degree, grin lens surface 805 be set with respect to 807 one-tenth about 7 degree of light propagation axis.In one embodiment, optical fiber input end 615 is also tiltedly polished, thereby optical fiber input end 615 is set in mode with respect to light propagation axis 807 values of acutangulating 811.In order to make the optically-coupled between grin lens 800 and the optical fiber 102 reach maximum, with respect to light propagation axis 807, the angle value of grin lens surface 805 and optical fiber input end 615 equates substantially.
By changing the structure of grin lens surface 805 and/or optical fiber input end 615, as shown in Figure 8, reduced the interference of the folded light beam 292 (from magneto-optic disk 107) of parasitic reflection E (t) and carrying signal significantly, because these two reflections spatially separate.
By after the polarization beam apparatus 239, beam component 292 ' (from folded light beam 292) also with noise component E ' (t) (from parasitic reflection E (t)) spatially separate.Beam component 292 ' (also referring to Fig. 2 a), (Fig. 2 a) through difference detector 240 processing again by the reception of one of magneto-optic (MO) detector lens 815 and photodiode 236 then.Similarly, after passing through polarization beam apparatus 239, beam component 292 ＂ (from folded light beam 292) and noise component E ＂ (t) (from parasitic reflection E (t)) spatially separate.(also referring to Fig. 2 a), (Fig. 2 a) through difference detector 240 processing again by the reception of one of MO detector lens 820 and photodiode 236 for beam component 292 ＂ then.
By means of using an opaque element (not shown) that is in the light that comprises an aperture can prevent that noise component E ' from (t) entering difference detector 240.Like this, the reflected beam components 292 of carrying signal ' will propagate is by aperture and enter difference detector 240 (Fig. 2 a), and the opaque element that is in the light will stop noise component E ' (t).Similarly, can use another opaque element that is in the light to stop noise component E ＂ (t), allow beam component 292 ＂ of carrying signal to spread into difference detector 240 simultaneously.
Change a kind of way, in optical system, use the opaque element that is in the light.If between the folded light beam 292 of reflection E (t) and carrying signal little angle tilt is arranged, then two ripples will make ups and at space interference pattern of place, photoelectric detector plane generation.The cycle of interference figure is provided by the Bragg relational expression: Δ g=λ/(2sin θ), θ is the half-angle between reflection E (t) and light beam 292 here.In the embodiment of Fig. 8, polarization beam apparatus in Differential Detection system 240 239 is placed before MO detector lens 815 and 820, thereby (Fig. 2 a) will have identical polarization, and this will cause the strength Interference effect to drop on MO detecting device (photodiode) 236 two light beams on any one.For example, in Fig. 8, the half-angle at MO detecting device 236 places is approximately 10 degree, and it is corresponding to about 1.9 microns grating cycle.For the MO detector size of about 300-400 micron, generally will detect mean intensity, thereby will make the laser noise influence reduce to minimum by each MO detecting device 236.
Implement the oblique polishing of grin lens and/or optical fiber input end 615 by for example using various oblique burnishers (they can be buied from the UltraTee of California axle Santa Ana).Also can use other suitable burnishers to change grin lens surface 805 and/or optical fiber input end 615.
Change a kind of way, can cut sth. askew to optical fiber input end 615 and cut, thereby with respect to light propagation axis 807 acutangulate modes it to be set.A kind of suitable device that is used for cutting optical fibre incident end 615 is that this equipment can be buied from the Newport Corporation of California Irvine by the FK12 type that the York Corperation of the United Kingdom the makes cutter of cutting sth. askew.
Optical fiber head end reflection (noise)
Referring now to Fig. 9 a,, appears at the parasitic reflection E at optical fiber head end 900 places of optical fiber 102 with discussion H(t).As the result of following reflection and produce parasitic reflection E H(t): (1) is in the reflection of head end from optical fiber surface 900 outgoing beams 291, or (2) are in the reflection of head end other optical element surface from some.Parasitic reflection E H(t) propagate towards photoswitch 104, and can interact, in sense channel, to produce superfluous noise with the Returning beam 292 of carrying signal.The character of noise depends on the type of the lasing light emitter that calls.If use the FP diode laser, then Mode Partition Noise (MPN) is main noise source.Because parasitic reflection E H(t) with detection module in back light 292 combination of carrying signal before the different optical path length of having advanced, therefore produced MPN.If the use Distributed Feedback Laser is then no longer relevant with MPN, but the mixing of the light by parasitic reflection and carrying signal, media noise can be exaggerated.In addition, when using the DFB lasing light emitter, little path difference can cause superfluous laser phase noise.Therefore, importantly implement a kind of technology, to eliminate (or significantly reducing) this undesired parasitic reflection.
Head end 900 places that are used at optical fiber 102 are discussed are now eliminated parasitic reflection E HThe various technology of influence (t).These technology comprise cut sth. askew cut or tiltedly polishing, refractive index match with do not have fiber core (or multimode) optical fiber and be connected.When using various types of lasing light emitters (such as FP laser instrument or Distributed Feedback Laser), can use these technology to transmit light by optical fiber 102.
The cutting sth. askew of influence that is used to reduce 900 reflections of optical fiber head end cut
According to an alternative embodiment of the invention,, optical fiber head end 900 cuts the parasitic reflection E that eliminates from the head end 900 of optical fiber 102 by being cut sth. askew H(t) influence.The angular dimension that cuts with respect to cutting sth. askew of light propagation axis 910 (Fig. 9 c) that the optical fiber head end is done has determined the size of the parasitic reflection that goes back towards 615 couplings of optical fiber input end.In Fig. 9 b, curve map 902 illustrates from the relative volume reflection of optical fiber head end 900 and the optical fiber head end relation with respect to the corner cut of light propagation axis 910.If for example optical fiber is not cut sth. askew with respect to light propagation axis 910 and is cut, then about 100% parasitic Fresnel reflection E H(t) the incident end 615 towards optical fiber 102 reflects back.As another example,, optical fiber head end 900 cuts (Fig. 9 c), then about 55% parasitic reflection E if cutting sth. askew with about 2 degree with respect to light propagation axis 910 H(t) the incident end of reflected back optical fiber 102.If it is optical fiber head end 900 is cut sth. askew and cut (Fig. 9 c) with about 4 degree with respect to light propagation axis 910, then about less than 10% parasitic reflection E H(t) the incident end 615 towards optical fiber 102 reflects back.Preferably optical fiber head end 900 is cut sth. askew in the scopes of extremely about 15 degree of about 6 degree with respect to light propagation axis 910 and cut, thereby propagate the parasitic reflection E that goes back towards the incident end 615 of optical fiber 102 H(t) disappear basically.Also can apply antireflection (AR) coat, its objective is the Fresnel reflection that further reduces at optical fiber head end 900 places optical fiber head end 900.
Fig. 9 c illustrates the optical fiber 102 with head end 900, cuts with respect to the angle of light propagation axis 910 about 8 degree this head end is cut sth. askew.Tiltedly cut value 903 make the central ray of outgoing beam with respect to light propagation axis 910 with an acute angle value 905 (for example, 4.0 spend) from head end 900 outgoing.Outgoing beam is as folded light beam 291 ' from steerable micro-machined mirror assembly 400 reflections, this folded light beam is propagated by object lens 446, and is directed to surface recording layer 349 place of magneto-optic disk 107 then.For folded light beam 291 ' guide surface recording layer 349 into along the direction of perpendicular, shown in Fig. 9 c, steerable micro-machined mirrors sub-component 400 with respect to light propagation axis 910 with suitable angle 915 (for example, about 43.0 degree) orientation.In one embodiment, the measured value of angle 915 be one be not 45 the degree the acute angle values.Folded light beam 291 ' vertically guide recording layer 349 into, thus light coupling effectively between optical fiber 102 and magneto-optic disk 107.In addition, in order to obtain optical fiber coupling maximal value, can be along the position of X, Y and/or Z direction adjusting optical fiber 102.
Notice that in Fig. 9 c, what head end 900 was cut sth. askew and cut faces down.In being shown in another embodiment of Fig. 9 d, optical fiber 102 has facing up of head end 900 ' cut sth. askew and cut.As a result, the angle 915 of steerable micro-machined mirrors assembly 400 is set with suitable value, thereby folded light beam 291 ' vertically guide into the recording surface 349 of magneto-optic disk 107.
Change a kind of way, by oblique polishing, can change optical fiber head end 900 (Fig. 9 c) and/or optical fiber head end 900 ' (Fig. 9 d) with respect to light propagation axis 910, tiltedly the mode of polishing is to top described similar with reference to Fig. 8.
On the contrary, if the head end 900 of optical fiber 102 is not cut sth. askew and does not cut (or tiltedly polishing), then the central ray of outgoing beam 291 in the mode that is parallel to light propagation axis 910 substantially from head end 900 outgoing, shown in Fig. 9 e.For folded light beam 291 ' guide surface recording layer 349 into, generally be about 45 degree with respect to the angle value 915 of light propagation axis 910 with vertical substantially orientation.If: (1) uses Distributed Feedback Laser, and (2) media noise and laser phase noise can ignore, and the optical system that then is shown in Fig. 9 e is useful especially.
Be used to reduce the refractive index match of light head end 900 reflections
According to an alternative embodiment of the invention, by the parasitic reflection E of refractive index match method elimination from the head end 900 of light 102 H(t) influence.Shown in Figure 10 a, the part of optical fiber 102 for example is fixed in the slide block 1000 by cementing agent 1005.Glass sheet 1010 is placed in the slide body 1000 with the orientation perpendicular to optical fiber 102 substantially.Fill with epoxy resin, fluid or gel 1015 or other suitable materials in space between optical fiber head end 900 and the glass sheet 1010, and the refractive index of these materials equates substantially with the refractive index of optical fiber fiber core.Under the unmatched condition of refractive index of the refractive index of the fiber core of optical fiber 102 and index-matching material 1015, the refractive index difference of admissible Δ n=± 0.05 between optical fiber 102 fiber cores and index-matching material 1015 causes about 0.03% surface reflections rate maximal value thus.
Shown in Figure 10 b, refractive index match fluid 1015 makes parasitic reflection E H(t) do not appear at optical fiber head end 900 places.And parasitic reflection E H(t) surface 1012 (that is, non-conjugated surface) that will appear at glass sheet 1010 is located, and the second parasitic reflection E ' H(t) will appear at non-conjugated surperficial 1013 places.As a result, parasitic reflection E H(t) and E ' H(t) be not coupled and return optical fiber.Because from optical system, removed parasitic reflection E effectively H(t) and E ' H(t), thus difference detector 240 (Fig. 2 a) can detect carrying signal folded light beam 292 component and not can with parasitic reflection E H(t) and E ' H(t) disturb mutually.
Be used to reduce optical fiber head end 900 reflection E H(t) optical fiber connects
According to an alternative embodiment of the invention, use the another kind of refractive index match method of discussing with reference to Figure 114 and 11b to eliminate parasitic reflection E from the head end 900 of optical fiber 102 H(t).At first, on the head end of optical fiber 102, connect no fiber core fiber segment 1100 referring to Figure 11 a.No fiber core fiber segment 1100 for example can have the diameter (for example, 80 micron) similar to single-mode fiber 102, and for example is coupled to optical fiber 102 by welding.Then no fiber core fiber segment 1100 along straight line 1105 cutting, thereby a part 1110 of 1100 of not having fiber core fiber segment is separated with part 1115.So part 1115 keeps being connected with optical fiber 102.In another embodiment, can use big fiber core multimode optical fiber (not shown), to replace no fiber core optical fiber.The length of the fiber section 1115 that connects is preferably selected, thereby the radius of the outgoing beam of exporting at face 1120 places of part 1,115 291 is less than the diameter of no fiber core optical fiber 102.Part 1115 for example can have about 100 microns length.The refractive index of the refractive index of no fiber core fiber section 1100 (and part 1115) and the fiber core of optical fiber 102 is mated substantially.Under the unmatched condition of refractive index of the refractive index of the fiber core of optical fiber 102 and fiber section 1115, the refractive index difference of admissible Δ n=± 0.05 between the fiber section 1115 of optical fiber 102 fiber cores and connection causes about 0.03% surface reflections rate maximal value thus.As a result, as discussed below, because refractive index match has significantly reduced the influence from the reflection of conjugate points (that is, head end 900).In addition, the light wave space distribution of outgoing beam 291 is not damaged at shape (for example, circularity) aspect.In addition, if the AR coat is placed on the connection optical fiber surface 1120, then can force down 0.25% to the Fresnel reflection from surface 1120, this causes the optical system of Figure 11 a a kind of more effective (that is low-loss).
If during connection procedure, the fiber core size at (optical fiber 102) head end 900 places changes owing to head end 900 is heated, then the equivalent mode field diameter of optical fiber 102 will increase.As a result, can supply with suitable object lens, compensate the increase of equivalent mode field diameter.
Shown in Figure 11 b, the fiber section 1115 of welding makes parasitic reflection E H(t) do not locate to occur at fiber end face (head end 900).And parasitic reflection E H(t) will occur at the interphase place between the air space of surface 1120 and vicinity.As a result, parasitic reflection E H(t) can not be coupled effectively and return optical fiber 102, thereby be eliminated effectively.Because from optical system, eliminated parasitic reflection E in fact H(t), thus difference detector 240 (Fig. 2 a) with can detection of reflected the component of laser beam 292, and not with parasitic reflection E H(t) interference.
Figure 11 c is a curve map 1150, and it illustrates from the relation of the length of the reflection of the head end 900 of optical fiber and welding optic fibre part 1115.This illustrates, if welding optic fibre part 1115 has the length at least about 100 microns, and the parasitic reflection E that then can reduce significantly at optical fiber head end 900 H(t) and the interference between the laser beam 292.
According to an alternative embodiment of the invention, if lasing light emitter 231 usefulness Distributed Feedback Lasers realize, and if in the optical system that discloses in the above media noise and laser phase noise both enough low, then do not need the above-mentioned technology that is used to eliminate the head end reflection.
Be appreciated that and can in multiple environment, find use of the present invention, such as the CD-ROM drive of other type, communication system, or the like.Therefore, though described the present invention here, in above-mentioned announcement, can make an amendment, various variation and substitute, and be appreciated that with reference to specific embodiments, in some example, can not depart from scope of the present invention and use some feature of invention but correspondingly do not use other feature.

Claims (100)

1. system that is used between lasing light emitter and memory location propagating main optical signal comprises:
An optical element that is arranged between lasing light emitter and the memory location and is suitable for sending the main optical signal that produces by lasing light emitter, this optical element comprises an end face;
It is characterized in that, construct this system and reduce interference between main optical signal and the parasitic signal that the parasitic signal is to be produced by the part from the main optical signal of the end face reflection of optical element.
2. the system as claimed in claim 1 is characterized in that, provides main optical signal by the Fabry-Perot laser instrument.
3. system as claimed in claim 2 is characterized in that, with at least near the frequency modulation (PFM) Fabry-Perot laser instrument of 200 megahertzes.
4. the system as claimed in claim 1 is characterized in that, provides main optical signal by stable single-frequency laser source.
5. system as claimed in claim 4 is characterized in that, stable single-frequency laser source comprises the distributed feed-back lasing light emitter.
6. the system as claimed in claim 1 is characterized in that, optical element comprises low birefringent fiber.
7. the system as claimed in claim 1 is characterized in that, the end face of optical element is provided with near lasing light emitter.
8. system as claimed in claim 7 is characterized in that, with the main optical signal of special frequency modulation (PFM) by the lasing light emitter generation, to reduce the interference between main optical signal and the parasitic signal.
9. system as claimed in claim 8 is characterized in that, optical element has the length relevant with special frequency.
10. system as claimed in claim 6, it is characterized in that, with specific frequency F=c (2i+1)/4Ln the main optical signal that is produced by lasing light emitter is done pulsed modulation, wherein, c is the light velocity in the vacuum, and L is the length of optical element, and n is the refractive index of optical element, and i is integer, and its value is at least zero.
11. system as claimed in claim 7 is characterized in that, between end face and lasing light emitter material is set, the refractive index that this material has substantially with the refractive index match of the fiber core of optical element, to reduce the interference between main optical signal and the parasitic signal.
12. system as claimed in claim 11 is characterized in that material comprises epoxy resin.
13. system as claimed in claim 11 is characterized in that material comprises fluid.
14. system as claimed in claim 7 is characterized in that, also comprises:
A container that is arranged between lasing light emitter and the optical element, comprise a kind of end face of optical element and material between the lasing light emitter of being arranged on, the refractive index that this material has substantially with the refractive index match of the fiber core of optical element, to reduce the interference between main optical signal and the parasitic signal.
15. system as claimed in claim 7 is characterized in that, between end face and lasing light emitter cover plate is set, the refractive index that cover plate has substantially with the refractive index match of the fiber core of optical element, to reduce the interference between main optical signal and the parasitic signal.
16. system as claimed in claim 7 is characterized in that, also comprises:
A container that is arranged between optical element and the lasing light emitter, comprise one and be arranged on the end face of optical element and the cover plate between the lasing light emitter, the refractive index that this cover plate has substantially with the refractive index match of the fiber core of optical element, to reduce the interference between main optical signal and the parasitic signal.
17. system as claimed in claim 7 is characterized in that, changes the structure of the end face of optical element, to reduce the interference between main optical signal and the parasitic signal.
18. system as claimed in claim 7 is characterized in that, end face is done tiltedly polishing, to reduce the interference between main optical signal and the parasitic signal.
19. system as claimed in claim 7 is characterized in that, also comprises:
Lens that are arranged between end face and the lasing light emitter, it comprises a sensitive surface, wherein, changes the structure of described sensitive surface, to improve the coupling efficiency of optical element.
20. system as claimed in claim 7 is characterized in that, sensitive surface is done tiltedly polishing, to improve the coupling efficiency of optical element.
21. the system as claimed in claim 1 is characterized in that, the close memory location of the end face of optical element setting.
22. system as claimed in claim 21 is characterized in that, the structure that changes the optical element end face is to reduce the interference between main optical signal and the parasitic signal.
23. system as claimed in claim 21 is characterized in that, the end face of cutting sth. askew is to reduce the interference between main optical signal and the parasitic signal.
24. system as claimed in claim 23 is characterized in that, also comprises:
A mirror assembly, it is arranged between end face and the memory location, and the angle of its orientation is not 45 degree with respect to the light propagation axis.
25. system as claimed in claim 21, it is characterized in that, a kind of material is arranged between end face and the memory location, the refractive index of this material substantially with the refractive index match of the fiber core of optical element, to reduce the interference between main optical signal and the parasitic signal.
26. system as claimed in claim 21 is characterized in that, also comprises:
A container, it is arranged between optical element and the memory location, comprise a kind of material that is coupled to the end face of optical element, the refractive index of this material substantially with the refractive index match of the fiber core of optical element, to reduce the interference between main optical signal and the parasitic signal.
27. system as claimed in claim 21 is characterized in that, end face is coupled to a fiber section, the refractive index of this fiber section equals the refractive index of the fiber core of optical element, to reduce the interference between main optical signal and the parasitic signal.
28. system as claimed in claim 27 is characterized in that, described fiber section does not have fiber core.
29. the system as claimed in claim 1 is characterized in that, also comprises:
A light phase hysteresis device, it is provided with near optical element, and is suitable for compensating the stress that causes on optical element.
30. the system as claimed in claim 1 is characterized in that, also comprises:
A light polarization spinner, it is provided with near optical element, and is suitable for compensating the stress that causes on optical element.
31. a low noise optical element is used for propagating main optical signal between lasing light emitter and memory location, comprising:
An optical fiber with at least one end face;
It is characterized in that optical fiber is configured to be used for to transmit main optical signal and reduces interference between parasitic signal and the main optical signal.
32. low noise optical element as claimed in claim 31 is characterized in that main optical signal is provided by the Fabry-Perot laser instrument.
33. low noise optical element as claimed in claim 32 is characterized in that, with near the frequency of 200 megahertzes the Fabry-Perot laser instrument being modulated at least.
34. low noise optical element as claimed in claim 31 is characterized in that, provides main optical signal by stable single-frequency laser source.
35. low noise optical element as claimed in claim 34 is characterized in that, stable single-frequency laser source comprises the distributed feed-back lasing light emitter.
36. low noise optical element as claimed in claim 31 is characterized in that optical fiber comprises low birefringent fiber.
37. low noise optical element as claimed in claim 31 is characterized in that, end face is provided with near lasing light emitter.
38. low noise optical element as claimed in claim 37 is characterized in that, with specific frequency the main optical signal that comes self-excitation light source is modulated, to reduce the interference between parasitic signal and the main optical signal.
39. low noise optical element as claimed in claim 38 is characterized in that, optical fiber has the length relevant with specific frequency.
40. low noise optical element as claimed in claim 37, it is characterized in that, make the lasing light emitter pulse operation with specific frequency F=c (2i+1)/4Ln, here c is the light velocity in the vacuum, L is the length of optical element, n is the refractive index of optical element, and i has the integer that is at least zero value.
41. low noise optical element as claimed in claim 37 is characterized in that, end face is coupled to a kind of material, its refractive index substantially with the refractive index match of the fiber core of optical element.
42. low noise optical element as claimed in claim 41 is characterized in that material comprises epoxy resin.
43. low noise optical element as claimed in claim 41 is characterized in that material comprises fluid.
44. low noise optical element as claimed in claim 37 is characterized in that, the end face of optical fiber is coupled to cover plate, the refractive index of this cover plate substantially with the refractive index match of the fiber core of optical fiber.
45. low noise optical element as claimed in claim 37 is characterized in that, changes the structure of the end face of optical fiber, to reduce the interference between parasitic signal and the main optical signal.
46. low noise optical element as claimed in claim 45 is characterized in that, end face is tiltedly polished.
47. low noise optical element as claimed in claim 37 is characterized in that, end face is positioned near having the lens part of a light receiving surface, at this receiving plane of textural change, to improve the coupling efficiency of optical element.
48. low noise optical element as claimed in claim 47 is characterized in that, light receiving surface is tiltedly polished.
49. low noise optical element as claimed in claim 31 is characterized in that, the end face of optical element is near the memory location.
50. low noise optical element as claimed in claim 49 is characterized in that, at the end face of textural change optical element, to reduce the interference between parasitic signal and the main optical signal.
51. low noise optical element as claimed in claim 50 is characterized in that, changes end face by means of cutting sth. askew.
52. low noise optical element as claimed in claim 50 is characterized in that, be provided with mirror assembly near end face, and the angle of its orientation is not 45 degree with respect to the light propagation axis.
53. low noise optical element as claimed in claim 49 is characterized in that, end face is coupled to a kind of material, the refractive index of this material substantially with the refractive index match of the fiber core of optical fiber, to reduce the interference between parasitic signal and the main optical signal.
54. low noise optical element as claimed in claim 53 is characterized in that material comprises fluid.
55. low noise optical element as claimed in claim 49 is characterized in that, end face is coupled to fiber section, the rate of penetrating of this fiber section folding substantially with the refractive index match of optical fiber fiber core, to reduce the interference between parasitic signal and the main optical signal.
56. low noise optical element as claimed in claim 55 is characterized in that, fiber section is no fiber core.
57. low noise optical element as claimed in claim 31 is characterized in that, optical fiber is provided with near light phase hysteresis device, and it is suitable for compensating the stress that produces on optical fiber.
58. low noise optical element as claimed in claim 31 is characterized in that, optical fiber is provided with near the light polarization spinner, and it is suitable for compensating the stress that produces on optical fiber.
59. an optical system that is used for transmitting main optical signal between light source and medium is characterized in that, comprising:
Optical fiber, it is suitable for transmitting light between light source and medium, and has at least one fiber end face; And
Wherein, optical system is configured to be used for to reduce the influence of the reflection that occurs at fiber end face.
60. optical system as claimed in claim 59 is characterized in that, provides light by the Fabry-Perot laser instrument.
61. optical system as claimed in claim 60 is characterized in that, with at least near the frequency modulation (PFM) Fabry-Perot laser instrument of 200 megahertzes.
62. optical system as claimed in claim 53 is characterized in that, provides light by stable single-frequency laser source.
63. optical system as claimed in claim 62 is characterized in that, stable single-frequency laser source comprises distributed feed-back formula lasing light emitter.
64. optical system as claimed in claim 59 is characterized in that optical fiber comprises low birefringent fiber.
65. optical system as claimed in claim 59 is characterized in that, fiber end face is provided with near light source.
66., it is characterized in that light source is with specific frequency pulse formula work, to reduce the influence from the reflection of fiber end face as the described optical system of claim 65.
67. as the described optical system of claim 65, it is characterized in that, light source modulated with special frequency F=c (2i+1)/4Ln, wherein, c is the light velocity in the vacuum, and L is the length of optical fiber, n is the refractive index of optical fiber, and i is integer, and its value is at least zero.
68., it is characterized in that, with special material fiber end face is made refractive index match, to reduce influence from the reflection of fiber end face as the described optical system of claim 65.
69., it is characterized in that, with cover plate fiber end face is made refractive index match, to reduce influence from the reflection of fiber end face as the described optical system of claim 65.
70. as the described optical system of claim 65, it is characterized in that, change fiber end face, to reduce influence from the reflection of fiber end face.
71. optical system as claimed in claim 59 is characterized in that, fiber end face is near medium.
72. as the described optical system of claim 71, it is characterized in that, change fiber end face, to reduce influence from the reflection of fiber end face.
73., it is characterized in that, with special material fiber end face is made refractive index match, to reduce influence from the reflection of fiber end face as the described optical system of claim 71.
74., it is characterized in that, fiber end face is coupled to the multimode optical fiber part, to reduce influence from the reflection of fiber end face as the described optical system of claim 71.
75. one kind in CD-ROM drive lasing light emitter and the memory location between propagate the method for main optical signal, it is characterized in that, comprising:
Stride across optical element and transmit main optical signal with an end face; And
Reduce from the reflection of end face and the interference between the main optical signal.
76., it is characterized in that lasing light emitter comprises the Fabry-Perot laser instrument as the described method of claim 75.
77., it is characterized in that lasing light emitter comprises stable single-frequency laser source as the described method of claim 75.
78., it is characterized in that stable single-frequency laser source comprises distributed feed-back formula lasing light emitter as the described method of claim 77.
79., it is characterized in that optical element comprises low birefringent fiber as the described method of claim 75.
80., it is characterized in that end face is provided with near lasing light emitter as the described method of claim 75.
81. as the described method of claim 80, it is characterized in that, reduce step and comprise:
According to the length of optical element, light is carried out pulsed modulation with special frequency.
82. as the described method of claim 81, it is characterized in that, light carried out pulsed modulation with the frequency near 200 megahertzes at least.
83. as the described method of claim 80, it is characterized in that, reduce step and comprise:
A kind of material that is coupled to end face is provided, and the refractive index of the refractive index of this material and the fiber core of optical element is mated substantially.
84. as the described method of claim 80, it is characterized in that, reduce step and comprise:
The end face that has cover plate is provided, and the refractive index of the refractive index of this cover plate and the fiber core of optical element is mated substantially.
85. as the described method of claim 80, it is characterized in that, reduce step and comprise:
Change the structure of the end face of optical element.
86. as the described method of claim 85, it is characterized in that, change step and comprise:
The opposite end mirror polish, thus special angle value between the surface of end face and light propagation axis, formed.
87. as the described method of claim 85, it is characterized in that, change step and comprise:
The cutting end face, thus special angle value between the surface of end face and light propagation axis, formed.
88. as the described method of claim 85, it is characterized in that, also comprise:
Provide the end face that is positioned at optical element near lens, these lens have the light receiving surface through changing.
89., it is characterized in that the end face of optical element is near the memory location as the described method of claim 75.
90. as the described method of claim 89, it is characterized in that, reduce step and comprise:
Change the end face of optical element.
91. as the described method of claim 90, it is characterized in that, change step and comprise:
On the end face of optical element, cut sth. askew and cut.
92. as the described method of claim 89, it is characterized in that, reduce step and comprise:
End face is coupled to a kind of material, and the refractive index of the refractive index of this material and the fiber core of optical element is mated substantially.
93. as the described method of claim 89, it is characterized in that, reduce step and comprise:
End face is coupled to a fiber section, and the refractive index of the refractive index of this fiber section and the fiber core of optical element is mated substantially.
94. an equipment that is used for direct light between the lasing light emitter of CD-ROM drive and memory location is characterized in that, comprising:
Be used between lasing light emitter and memory location transmitting the device of light, the device that transmits light comprises an end face, and the device that transmits light also comprises the device that is used to reduce from the influence of the reflection of end face.
95. one kind is used for passing to data-storage system and goes laser beam and to transmit the low noise optical system of laser beam from data-storage system, it is characterized in that the low noise optical system comprises:
, a light path can pass to data-storage system and go laser beam and transmit laser beam from data-storage system, and light path has an end at least, and wherein, the low noise optical system is configured to be used for the reflection of mobile laser beam, with reduce to reflect and laser beam between interference.
96., it is characterized in that as the described low noise optical system of claim 95, move reflection according to the time, with reduce to reflect and laser beam between interference.
97., it is characterized in that as the described low noise optical system of claim 95, aspect the position, move reflection, with reduce to reflect and laser beam between interference.
98. one kind passes to data-storage system and to go laser beam and to transmit the method for laser beam from data-storage system, it is characterized in that, comprising:
Go laser beam and transmit laser beam to the data-storage system biography from data-storage system; And
The reflection of mobile laser beam, with reduce to reflect and laser beam between interference.
99., it is characterized in that mobile step comprises as the described method of claim 98:
Move reflection in time, with reduce to reflect and laser beam between interference.
100., it is characterized in that mobile step comprises as the described method of claim 98:
Spatially move reflection, with reduce to reflect and laser beam between interference.
CNB998046477A 1998-03-30 1999-03-30 Optical data storage system with means for reducing noise from spurious reflections Expired - Fee Related CN1160715C (en)

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US7990398P 1998-03-30 1998-03-30
US60/079,903 1998-03-30
US8819298P 1998-06-05 1998-06-05
US60/088,192 1998-06-05
US09/124,812 US6298027B1 (en) 1998-03-30 1998-07-29 Low-birefringence optical fiber for use in an optical data storage system
US09/124,812 1998-07-29
US10839898P 1998-11-13 1998-11-13
US60/108,398 1998-11-13
US11147098P 1998-12-09 1998-12-09
US60/111,470 1998-12-09
US09/281,753 1999-03-30
US09/281,753 US6587421B1 (en) 1998-03-30 1999-03-30 Refractive index matching means coupled to an optical fiber for eliminating spurious light

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